Continuous two-staged co-digestion process for biohydrogen production from agro-industrial wastes

Abstract

SUMMARYMexico produces large amounts of organic residues. Twenty milliard tons of fruit and vegetable wastes (FVW) are produced yearly. On the other hand, the cheese processing industry produces crude cheese whey (CCW) with an annual production of 1 million metric tons. These types of residues are well characterized, and both constitute a potential feedstock for biohydrogen production, individually or as a mixture. Recently, we demonstrated the feasibility of utilizing CCW and FVW in a co-digestion process to produce biohydrogen. The possibility to design an effective process in a two stage configuration was evaluated based in our previous studies of the by-products and description of microbial ecology evolution of the co-digestion process. An initial assimilation of easily degradable carbohydrates and protein allowed cell growth and acetate and lactate as main byproducts. The co-digestion and two-stage processes increased several times the biohydrogen yield compared with those obtained from single substrate and in a co-digestion single stage process. Higher biohydrogen productivity was a result of reaction stability in comparison to single-substrate digestion and one-stage processes.The effect of hydraulic retention time (HRT) and organic loading rate (OLR) on the volumetric hydrogen production rate (VHPR) and yield (Y H2 ) was evaluated in a two-staged co-digestion process of FVW and CCW. The system consisted of hydrolytic and hydrogenic bioreactors operated in batch mode and continuous regime (89 days), respectively. Eight conditions of HRTs and respective OLRs were evaluated. As HRT decreased, the VHPR increased proportionally, reaching the highest average values around 7 L L À1 d À1 at an HRT between 15 and 17.5 h. The highest Y H2, (813.3 mL H 2 g COD À1 ) was determined at 17.5 h (OLR, 80.02 g COD L À1 d À1 ). Based on the distribution of the final products, the processes occur sequentially and reach a steady state set by the OLR. Biohydrogen production is a result of a syntrophic microbial activity. In general, the two stages of the co-digestion process provided higher stability, reliability, and efficiency.

Dark fermentative hydrogen production from sucrose and molasses

“…Substrate source and its concentration, seed sludge source and pretreatment types, reactor configuration, hydraulic retention time, pH, organic loading rate, and temperature are among the operational factors that affect the dark fermentative hydrogen production. Parameters like pH, chemical oxygen demand (COD), hydraulic retention time, or organic loading rate are frequently investigated in dark fermentation studies [4,[10][11][12][13][14][15], and fairly consistent results are achieved in most studies. Usually, pH values from 4.5 to 6.0 were studied with the optimum value around 5.5 [13].…”

“…Homoacetogenic activity (consumption of H 2 and CO 2 by autotrophic acetogenic microorganisms) is also defined as a significant obstacle before achievement of high yield and stability in dark fermentative hydrogen production . Therefore, topics such as modification/optimization of the operational conditions, improvements in reactor design, pretreatment of the waste, application of two‐phase systems, microbial community enrichment and immobilization, and the use of genetically modified organisms are under development .…”

A Review on Biohydrogen Sources, Production Routes, and Its Application as a Fuel Cell

“…Lucas et al [65] produced biohydrogen using cassava wastewater, dairy wastewater, and citrus processing wastewater as sources and the production of hydrogen was found to be 31.41, 28.95, and 37.25 mL/g. Gomez-Romero et al [66] utilized fruit and vegetable wastes and crude cheese whey for the production of biohydrogen. The yield of produced hydrogen was 813.3 mL H 2 g COD −1 and was determined at 17.5 h (Hydraulic Retention Time) with an organic loading rate of 80.02 g COD L −1 d −1 .…”

Fermentative bio-hydrogen production using lignocellulosic waste biomass: a review

“…This effluent then acts as feedstock for the second stage called methanogenesis, where methane production occurs [45,47,49]. Many researchers have studied this type of two-stage process for hydrogen and methane production using different feedstock and different working conditions [49][50][51][52]. However, the two-stage fermentation also faces some obstacles like it yields very low hydrogen and methane yields when the feedstock used is lignocellulosic biomass.…”